This invention was conceived as a solution to the problem of providing a swing tower mechanism and backhoe assembly which possesses two advantages not found together in prior art machines. One advantage is improved balance, i.e., retraction closer to the tractor rear when the backhoe is being transported. The other is ready detachability of the backhoe.
As shown in my copending U.S. Pat. No. 4,720,234 , various backhoe arrangements have been devised in efforts to improve operator visibility and bring the center of gravity of the backhoe closer to the tractor when the backhoe is being transported. These are:
First, that of U.S. Pat. No. 3,376,984 to Long and Shumaker, featuring a boom and two outboard boom cylinders, all pivotally mounted on a swing tower so that the boom cylinders flank the boom in a clearance relationship; PA0 Second, that of U.S. Pat. No. 3,987,914 to VanDerZyl, McMullen and Kraske, in which the boom is constructed in two sections, with the boom cylinder having its cylinder side pivotally secured directly to the swing tower; PA0 Third, that of U.S. Pat. No. 4,074,821 to Long, featuring a boom cylinder and two outboard boom sections which flank the cylinder; and PA0 Fourth, that of U.S. Pat. No. 4,358,240 to Shumaker, in which the boom and boom cylinder are pivotally mounted in offset relation on a swing tower.
Each prior art structure suffers from one or more of the following limitations: Obstruction of the operator's view, lack of practical detachability, or insufficient achievement of good balance during transport of the backhoe. In providing a solution which is relatively free of the disadvantages and limitations of the prior art, I conceived of a swing tower mechanism in which the backhoe assembly proper is mounted on a rocker, which shifts the backhoe assembly between transport and working positions, making a substantial improvement in the balance of the tractor-backhoe ensemble. In the improved backhoe of my U.S. Pat. No. 4,720,234, I positioned the bucket on the ground and used thrust of the boom cylinder against the rocker to put the rocker in transport mode and enable the backhoe to go into transport position. I later conceived the idea that the rocker positioning could be controlled from the swing tower by mounting a rocker-control hydraulic cylinder on the swing tower. Then positioning of the rocker could be controlled without depending on the subordinate machine. This led to the perception that the combination of swing tower, rocker and rocker-actuating cylinder constituted the basis for a three-point hitch, so that now a tractor suitable for a backhoe could be used to support, transport, elevate and depress, lift, tow, move in azimuth or allow to move in azimuth, a wide range of subordinate machines; for example, the blade 52 of FIGS. 13 and 14. Optionally, a hydraulic motor with power-takeoff shaft can also be mounted on the rocker (FIGS. 11, 16, 17). Such a power takeoff, being carried by the rocker, automatically moves in elevation and azimuth with the subordinate vehicle or machine. Thus, the combination of swing tower, rocker, and hydraulic actuator, with the capacity to transport and position the rocker load, has very wide application.